The Colorback Mine I (previously Turquoise Boy mine) is North-Northwest of Tenabo near Crescent Valley, Nevada. Colorback Turquoise is associated with an opalized sill that dips into black chert. The chert adjacent to the sill is brecciated and contains the turquoise. The Colorback Mine II produces a beautifully white, tight, black spiderwebbed Chalcociderite as well as a gorgeous green and rare blue Varascite with a black or brown matrix.